Do not rely on ActiveSupport::JSON being loaded for this test model
Do not rely on ActiveSupport::JSON being loaded for this test model

Without it we're getting a couple errors with Ruby 3.0 and Rails 6 that
I couldn't track down on a quick search, but at the end of the day we
shouldn't be relying on ActiveSupport::JSON anyway to be present, we
just want to test that the model responds/serializes appropriately to
json method like the other methods.

plataformatec/responders,plataformatec/responders,plataformatec/responders